Documents of any kind are used to pay for goods. A rising number of goods, e.g. food, toys, medicine, tickets and so forth are available at vending machines. The customer can pay at these vending machines with documents, e.g. bills, banknotes or coupons. Further, document acceptors are also used in the gaming industries and in the banking sector. The received and accepted documents are typically stored within the machines in document cassettes. Stacking mechanisms are incorporated in the document acceptors to facilitate storage of the documents in the cassettes.
Various types of stackers are known. For example, commonly used piston-type stackers are described in US 2008/0128241 A1. Stackers with scissor mechanisms are described, for example, in EP 2 196 964 A1. It is generally desirable for the stacking mechanisms to have a simple construction and to be reliable in the operation of stacking documents. The more parts the respective stacker design has the more susceptible to failure is the stacking mechanism. Scissor type stacking mechanisms for example are built of a plurality of different parts and are therefore relatively expensive and complicated to assemble.
Another critical constraint of stacking mechanisms is the overall size of the mechanisms. This becomes particularly relevant when documents of different size shall be stacked within the same document cassette. On the one hand, the slot or gap through which the documents are pushed into the cassette has to be adapted to the smallest document to be stored so that the documents are safely retained in the cassette. On the other hand, the larger documents have to be folded during the insertion into the cassette and pushed relatively deep into the cassette to forward them entirely through the narrow gap adapted for the smallest documents to be inserted. This increases the required stroke of the, e.g., scissor or piston-type mechanism as well as the required force to fold the document and to push it deep into the cassette. An increased stroke in turn requires more space and an enhanced need of force for the stacking operation requires stronger and thus larger components for the stacking mechanism. Consequently, the overall size and weight of the stacking mechanism would be enlarged when trying to provide a stacking mechanism for different sizes of documents.
More generally, it would be helpful to have a stacking mechanism that has a robust and simple design on the one hand as well as a compact size and the ability to handle documents of a plurality of sizes on the other hand.